This invention relates to a process for the preparation of cationic paper sizing agents. More particularly, it relates to a process for reacting a copolymer of maleic anhydride and an .alpha.-olefin, with basic nitrogen compounds, and converting the resultant product to salt.
Many synthetic agents, as well as naturally occurring substances, are known to be useful as paper sizing agents. In addition to resins and resin soaps derived from rosin, waxes and paraffins, fatty acids and their salts, and many others, numerous synthetic agents such as alkaline solutions of condensation products of formaldehyde withh phenols, melamine formaldehyde resins, as well as compounds based on diketenes, polyurethanes, and the like, are recommended as sizing agents.
Reaction products of copolymers of maleic anhydride may be used as sizing agents, as taught in U.S. Pat. No. 3,853,609. Such compounds are obtained from a copolymer of maleic anhydride and .alpha.-olefins with 4 to 6 carbon atoms, as well as ammonia. In order to obtain sizing effect with the compounds described in said patent, it is necessary to utilize relatively high concentrations of the polymer. Also, the sizing effects obtained with such compounds are not satisfactory in many respects. The sizing agents utilized in U.S. Pat. No. 3,853,609 are also anionic in nature.
Cationic compounds useful for sizing paper, which are obtained by the reaction of copolymers of maleic anhyride with basic nitrogen compounds such as amines, are described for example in German patent disclosure 1,621,688, wherein maleic anhydride homo-or copolymers are reacted with N-dialkyl aminoalkyl amines, if necessary in mixture with ammonia or primary aliphatic or cycloaliphatic monoamines and, also if necessary, converted to a salt. However, to achieve noticeable sizing activities, such agents must be blended with homo- or copolymers of olefinic, unsaturated, polymerizable monomers, or chemically modified through further reaction.
Although there are many sizing agents of varied chemical compositions, there still exists a demand for improved products having high sizing activity which display a satisfactory aging resistance and compatibility with other auxiliary agents required in the manufacture of paper. It is also desirable to have such agents which are resistant to the influence of light, possess better processing characteristics, and in particular, result in good sizing at various pH values.